Sensor device and position determination process and their use for the control of an insertion robot

ABSTRACT

The sensor device includes a planar code carrier on one object, and on another object, a scanning device for an angle of view for determining a viewing direction lying therein, and also a computing circuit. A photodetector detects an illumination density during the course of the scanning of the angle of view according to the direction of light incidence. On the code carrier there is arranged a rectangular code field with its center line parallel to the scanning plane. The code field includes at least two rectangular positioning fields and a rectangular interfield lying in between. The positioning fields contain positional information on the objects which can be evaluated by the scanning device. In at least one interfield, the code includes at least one boundary line obliquely intersecting the center line, the scanning of which boundary line produces a distinct variation of the illumination density in dependence on the direction of light incidence, which corresponds to a viewing direction to be established. The interfield may be subdivided by a diagonal line into two optically identical interfield regions or by a boundary line diagonally into two optically different interfield regions, and this configuration may be mirror-symmetrically duplicated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sensor device for establishing the relativeposition of two mutually displaceable objects, a method of automaticallydetermining a position of a displaceable robot with respect to an objectwith the aid of the sensor device, and a use of the sensor device and anapplication of the method for controlling a mounting robot for a line ofmachines and/or devices, in particular for the automatic processing ortreatment of electronic chips.

2. Discussion of the Prior Art

FIG. 1 schematically shows in perspective a line of machines for theautomatic processing and/or of devices for the automatic treatment ofelectronic chips according to the prior art.

FIG. 2 shows in a schematic side view selected elements of theinstallation shown in FIG. 1 according to the prior art.

The journal "productronic 1/2-1991", page 112 and "EuropeanSemiconductor", October 1990, disclose the line of machinesschematically represented in perspective in FIG. 1 for the automaticprocessing and of devices for the automatic treatment of electronicchips. The machines B1-B4 are, for example, "die bonders" and "wirebonders" for establishing electrical connections on the chips, and thedevices E1-E2 are, for example, continuous furnaces for the curing ofplastics and devices for the intermediate storage of the chips. Thechips to be processed or to be treated are contained in magazines M whenthey are transported, fed to the machines B1-B4 or devices E1-E2 andprepared therein for processing or treatment and also for transportingaway after the processing or treatment.

The machines B1-B4 and devices E1-E2 are set up in series. Arrangedbehind this series, with regard to the transport of the magazines, is arail device T, on which there runs a mounting robot R, which grips,moves, positions and releases the magazines M as required.

In FIG. 2, the machine B1, the rail device T and the mounting robot Rare represented in a schematic side view. The mounting robot R travelsrectilinearly and horizontally on the rail device T. A gripper G for themagazine M is supported movably on the mounting robot R by means of anadvancing carriage V and a lifting carriage H. The advancing carriage Vis movable on the mounting robot R horizontally and orthogonally to therail device T towards the machine BI and away from it. The liftingcarriage H is movable vertically on the advancing carriage V.Consequently, the gripper G can be moved with three Cartesian degrees offreedom or directions of movement with respect to the machine B1 inorder to bring the magazine M to the intended magazine position P1 or P2at the machine B1 and unload it there, or to grip it there and lead itaway from there.

This entails the problem of automating the movements of the mountingrobot R.

The machines B1-B4 are namely set up, changed and adjusted in accordancewith the requirements of fabrication. The individual machines are thenadmittedly aligned as well as possible at right angles to the raildevice T or to the running direction of the mounting robot R, but arenot mechanically connected directly and in a predetermined way to therail device T. The only common reference is the floor plane; moreover,the machines M or their magazine positions P1-P2 may be arranged atvarious non-standardized heights above the floor and at variousnon-standardized distances from the rail device T. Under thesecircumstances, to automate the movements of the mounting robot R it isnecessary to make the mounting robot R itself learn the magazineposition P1-P2 and determine the corresponding set position of thegripper G, otherwise the magazine positions P1-P2 would have to bemeasured after each change and entered into the control of the mountingrobot R as a corresponding default value, which would be extremelycomplex. To detect the magazine positions concerned, sensor devices arenecessary.

A sensor device which can be used for this is disclosed, for example, bythe brochure "LN110/120" of the Namco company. It essentially comprisesa laser as light source, a constantly rotating mirror, a photodetectorand an angle-reference detector, which are all integrated in a measuringdevice, and also a retro-reflector and, if appropriate, code plates,which are attached on an object, and a microprocessor, one of thefunctions of which is that of a computing circuit. Using the constantlyrotating mirror, the laser beam periodically scans a predetermined angleof view. The retro-reflector returns the laser beam to thephotodetector. As long as the laser beam scanning at a constant ratemeets the retro-reflector, the photodetector generates aretro-reflection pulse, the duration of which is inversely proportionalto the distance of the retro-reflector from the photo-detector. Thecloser the retro-reflector is to the photodetector, the greater thepulse duty factor of retro-reflection duration to dark interval in aperiod of the scanning. On the other hand, the angle-reference detectorgenerates an angle-reference pulse with each period of the scanning. If,during the course of scanning, the laser beam reaches theretro-reflector, a retro-reflection pulse begins. The time between thebeginning of the angle-reference pulse and the beginning of theretro-reflection pulse is directly proportional to the angular positionof the retro-reflector with respect to the direction of the laser beamat the beginning of the angle-reference pulse. Consequently, the angularposition or the distance of the retro-reflector can be measuredcontactlessly, provided that the dimension of the retro-reflector in theplane of the scanning to the laser beam or orthogonally to the axis ofthe rotating mirror is known. If the known retro-reflector is,furthermore, arranged at a defined point of an object, or if a knownobject is arranged between the known retro-reflector and thephotodetector in such a way that it interrupts the laser beam, thecomputing circuit can calculate the distance and position of the objecton the same principle. In this case, there may be arranged on the objectadditional code plates, by which the computing circuit can identify theobject.

In the immediately following text, to simplify explanations it isassumed that an object or a code plate always lies in a plane orientedessentially orthogonally to the angle bisector of the angle of view. Ifthe object or code plate is oriented askew by a known angle to the anglebisector of the angle of view, the distances calculated by the computingcircuit from the object or code plate to the optical center of thesensor device are to be corrected by the sine of this angle.

If, in a line of machines for the automatic processing and of devicesfor the automatic treatment of electronic chips, the mounting robot R isprovided with a sensor device of the type specified above, the computingcircuit supplies the information specifying the distance and position ofthe machines B1-B4 and devices E1-E2, but only in the plane of thescanning with the laser beam or orthogonally to the axis of the rotatingmirror. To automate the movements of the mounting robot R there is stillmissing the information in the direction parallel to the axis of therotating mirror or orthogonally to the plane of the scanning with thelaser beam, since the information obtained with a sensor device of thetype specified above is only two-dimensional, which is inadequate forautomating the movements of the mounting robot R.

To overcome this inadequacy by combining two sensor devices of the typespecified above is complex and, furthermore, disruptive owing to therestricted space around the mounting robot.

SUMMARY OF THE INVENTION

The object of the invention is to improve a sensor device of the typespecified above in such a way that a single sensor suppliesthree-dimensional information which suffices in particular forautomating the movements of the robot.

With the sensor device according to the invention, a single scanningdevice suffices for positioning the mounting robot with the aid of acode field according to the invention and, if appropriate, also forreading information in additional code fields.

The invention makes it possible on the one hand to make the computingcircuit establish from the machines or devices and from the magazinestheir positions and dimensions simply and, if appropriate, in anautomatically proceeding operation in order for these to be passed on asinformation to the control of the mounting robot. The mounting robotlearns the positions and dimensions of the machines or devices andmagazines simply and, if appropriate, in an automatically proceedingoperation. Thereafter, the various positions of magazines at the variousmachines or devices can be moved automatically by the gripper and thevarious magazines can be handled according to their type.

On the other hand, it is possible with the invention to provide on themachines, devices and magazines, on the same or other code carriers,additionally and in a predetermined position in relation to the codefield according to the invention further code fields, which supplyinformation, for example on the type of a machine, of a magazine and thelike. Because the mounting robot knows the positions of the additionalcode fields in relation to the code field according to the invention, assoon as it has learned the positions and dimensions of the machines ordevices and magazines it is possible for it also to bring the furthercode fields into the angle of view of the scanning device in order toread their information.

Each time positions are moved to by the gripper these positions can,moreover, be checked automatically by comparison of the newlyestablished actual position with the stored set position. The result ofthis check can be used for automatically correcting distance errors,which are attributable, for example, to the great length of the seriesof machines or devices, and displaced positions, which are caused, forexample, by unintended displacing of the machines or devices or bymovements and vibrations of the ground, the originally learned positionsbeing correspondingly adjusted. The result of the check can also be usedfor detecting the absence of certain positions or items, if, forexample, at a position for magazine reception no place is ready for anadditional magazine or at a position for magazine discharging nomagazine is ready.

Finally, objects which are not programmed in the control of the mountingrobot can be detected as such, which allows this control to avoidcollisions of the mounting robot with obstacles, such as displacedmagazines, hanging-down cables, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below with reference to theattached drawings. Further advantages of the invention are also evidentfrom this description.

In the drawings:

FIG. 1 schematically shows in perspective a line of machines for theautomatic processing and/or of devices for the automatic treatment ofelectronic chips according to the prior art; and

FIG. 2 shows in schematic side view, selected elements of the prior artline shown in FIG. 1.

FIG. 3 shows a plan view or a retro-reflector with the bar codeaccording to the invention as a mask, for use with the known sensordevice of the type specified above;

FIG. 4 shows a geometrical diagram of the angle and length relationshipsof bar code and light beam in the sensor device;

FIGS. 5a and 5b each show a geometrical diagram of the angle and lengthrelationships of boundary lines and surface areas in an intermediatefield with a diagonal line and two optically identical intermediatefield regions; and

FIGS. 6a and 6b each show a geometrical diagram of the angle and lengthrelationships of boundary lines and surface areas in an intermediatefield with two optically different intermediate field regions.

DETAILED DESCRIPTION

In FIG. 3, a retro-reflector 1, known per se and described, for example,in the already cited Namco brochure, is represented in plan view ontoits essentially planar retro-reflecting surface. The retro-reflector 1is part of a sensor device, for example of the type described in thecited Namco brochure. This sensor device is, for example, attached on arobot, such as the mounting robot R represented in FIGS. 1 and 2.

In principle, instead of a retro-reflector, a surface scattering thelight in a suitable way, i.e retro-diffusion instead ofretro-reflection, may also be used, and, instead of a laser beam, adifferent type of light beam may be used. Also, instead of a periodicscanning with laser light and a mirror rotating about an optical center,a global scanning may be used with light from a row of LEDs with use ofa row of photodetectors.

Attached on the retro-reflecting surface of the retro-reflector 1 is anessentially planar mask, which has at certain points opaque thickbar-shaped lines 2 and opaque thin bar-shaped lines 3, and istransparent at its other points. The mask is, for example, aphotographic emulsion coating on a glass plate, which for its part islaid over the retro-reflecting surface. The mask may, however, also bepainted directly with coloring on the retro-reflecting surface of theretro-reflector 1. In principle the glass plate may also be arranged infront of the retro-reflecting surface. The opaque lines areadvantageously black, in order also to be better perceivable by the eye.

The retro-reflector 1 with the applied mask is arranged at apredetermined point on the rear side of each machine and device of FIG.1, for example at the point S in FIG. 2, at a predetermined height abovethe ground. This height is entered into the computing circuit of therobot as a corresponding default value and is consequently known by thecontrol of the robot, so that it is possible for it to move the robot insuch a way that the retro-reflector 1 comes into the angle of view ofthe sensor device.

Furthermore, the computing circuit of the robot is informed by acorresponding default value where in the case of a certain type ofmachines or devices the individual points of significance, in particularthe positions at which magazines are to be brought or picked up, arelocated in relation to the retro-reflector 1. Thus, as soon as thecomputing circuit of the robot becomes aware in the way explained belowof the position of the retro-reflector 1, it is possible for the controlof the robot to make the gripper move automatically to the positionsmentioned and to handle the various magazines in accordance with theirtype.

On the retro-reflector 1, the combination of lines, such as the lines 2and 3, form various bar codes, which can be scanned by the light beam ofthe sensor device. For this purpose, the lines, as usual in the case ofbar codes, are divided into groups of lines each with a coded meaning inthe combination of lines, and each group of lines is arranged withinvirtual, (i.e. not provided with an actual border) rectangular linegroup regions, in order to form an information block.

In the exemplary embodiment of FIG. 3, four particular line groupregions 6A, 6B, 6C, 6D together form a virtual (i.e. not provided withan actual border) essentially rectangular code field. Theretro-reflector 1 is arranged on a machine or device of FIG. 1 in such away that a center line of the rectangular code field lies essentiallyparallel to a scanning plane of the sensor device (the center line of arectangle is generally a geometrically well-defined term, but in thepresent design of the invention not an actually existing line, for whichreason the center line mentioned has not been drawn in FIG. 3).

In the rectangular code field, each of the line group regions 6A, 6B,6C, 6D itself forms a virtual (i.e. not provided with an actual border)rectangular positioning field, to be precise in such a way that therectangles concerned, virtually bordering the groups of lines, areidentical. Moreover, the groups of lines are oriented in theirrectangles or line group regions 6A, 6B, 6C, 6D in such a way that ineach case a longer border of the rectangle or line group region, such asthe border 7 or 12, is also a longer border of a line. Finally, therectangles or line group regions 6A, 6B, 6C, 6D are arranged withrespect to one another in such a way that their virtual (i.e. notrepresented by an actual line) short sides are aligned congruently andtheir long sides lie parallel to one another (incidently, the terms"long" and "short" refer to the particular representation according toFIG. 3, but they may be interchanged within the scope of the invention).Incidently, the code in a positioning field respectively comprises agroup of lines of at least two rectangular lines and a rectangularinterspace lying in between, the lines and interspaces differingoptically from one another, for example such as light and dark, andtheir longitudinal direction running at right angles to the center lineof the code field over the entire extent of the latter.

The respectively neighboring rectangular positioning fields or linegroup regions 6A and 6B, or 6B and 6C, or 6C and 6D, are arranged at thesame predetermined distances from one another, so that in between ineach case the same virtual (i.e. not provided with an actual border)rectangular interfields 8AB, 8BC, 8CD are defined. The code field isthus filled exactly by a sequence, alternating along the center line,positioning fields 6A, 6B, 6C and 6D and interfields 8AB, 8BC, 8CD.

The positioning fields or line group regions 6A, 6B, 6C, 6D form aseries. Each group of lines is coded for the position of the line groupregion 6A, 6B, 6C, 6D concerning them in the series, preferably with anumber from a series of consecutive numerical values. In the exemplaryembodiment according to FIG. 3, the line group region 6A is coded by thenumber 0, the line by group region 6B by the number 1, the line groupregion 6C by the number 2 and the line group region 6D by the number 3.Altogether, the code arranged in a positioning field thus corresponds toa position of this positioning field in the code field, and this codecomprises positional information which can be evaluated by the scanningdevice and specifies at which point the positioning field is located ina sequence formed by the positioning fields along the center line, thesuccessive positions of the positioning field in the code fieldpreferably being expressed by consecutive numerical values.

Arranged in each of the rectangular interfields 8AB, 8BC, 8CD there isin each case a diagonal line 9AB, 9BC, 9CD, which joins the mutuallydiagonally opposite ends of mutually opposite borders of the neighboringpositioning fields or line group regions, as for example the diagonalline 9BC joins an end 10 of the border 7 of the line group region 6Cwith an end 11 of the border 12 of the line group region 6B. Thediagonal line 9AB, 9BC, 9CD represents in the respective interfield 8AB,8BC, 8CD a boundary line, obliquely intersecting the center line,between two surface areas of the interfield. During the scanning of thisboundary line by the scanning device, the brightness contrast betweenthe interfields and the diagonal line produces in the scanning device avariation of the illumination density, to be correct two rapidlysucceeding opposed variations of the illumination density, which permitsa determination of the viewing direction, which is explained in moredetail below in conjunction with FIG. 4.

The arrangement described above as an example, of four positioningfields or line group regions 6A, 6B, 6C, 6D and three diagonal lines9AB, 9BC, 9CD in the respective interfield 8AB, 8BC, 8CD, may readily beextended to a higher, but preferably even number of line group regionsand the corresponding, one less, odd number of preferably mutuallyparallel diagonal lines.

The diagonal lines 9AB, 9BC, 9CD, as represented in FIG. 3, arepreferably oriented parallel to one another, although this is notobligatory if the computing circuit has the information necessary forfurther processing.

With regard to the description of the method according to the inventionof automatically positioning the robot with respect to theretro-reflector with the mask lined thereupon, it is first of allexpedient to explain the geometrical diagram represented in FIG. 4 ofthe angle and length relationships of bar code and light beam in thesensor device.

The basis taken for this (in particular because of the simplergeometrical relationships) is the known scanning device, for exampledescribed in the already cited Namco brochure. In principle, however,the periodic scanning known from the latter with laser light and amirror rotating about an optical center could be replaced by a globalscanning with light from a row of LEDs with use of a row ofphotodetectors, without departing from the principle of the explanationswhich follow.

In FIG. 4, a wall 40 of a machine or device on which the retro-reflector41 is arranged is schematically represented. Arranged on theretro-reflector 41 is the mask 42, which bears the bar code, of whichonly a point 43 of a diagonal line, such as the diagonal lines 9AB, 9BCor 9CD of FIG. 3, is represented.

The light beam emanates from the point 44 and is sent back to the point44 by the retro-reflector 41, unless this is prevented by the bar codeof the mask 42. The point 44 thus has in the diagram of FIG. 4 thesignificance of an optical center of the sensor device. Theretro-reflector 41 and the mask 42 are represented in the diagram ofFIG. 4 with a considerable thickness, but this serves only that theretro-reflector 41 and the mask 42 can be seen and in the following isinsignificant and need not be paid any attention.

On account of the deflection of the light beam by the constantlyrotating mirror, the light beam moves continuously about the point 44,for example in the clockwise sense. The angular positions of the lightbeam are measured positively in the clockwise sense in FIG. 4, theirzero value lying at an angular position predetermined in the sensordevice by the angle-reference detector, which position is represented inFIG. 4 by the reference direction 45. During the course of a rotationalperiod of the mirror, the angular position increases in the direction ofthe arrow 46 about the point 44 from a value at the beginning (notshown) of the angle of view at a time t_(A), via a value at thebeginning of the scanning of the mask at the line 47 at a time t_(U) andthereafter a value at the end of the scanning of the mask at the line 48at a time t_(V), up to a value (not shown) at the end of the angle ofview at a time t_(E). In this case, the angular position coincides withthe angle bisector of the angle of view at a time t_(W) whichcorresponds to the equation t_(M) =1/2(t_(E) -t_(A)). This operation isrepeated with every revolution of the constantly rotating mirror, whichleads to periodic scanning of an angle of view predetermined by thedesign of the sensor device.

As already mentioned, to simplify the explanations which follow it isassumed that the retro-reflector 41 and the mask 42 lie in a planeoriented essentially orthogonally to the angle bisector of the angle ofview. Consequently, the angle bisector of the angle of view coincideswith the normal 49 of the optical center 44 to the retro-reflector 41and to the mask 42.

Because the computing circuit of the robot is known as the correspondingdefault value at which height above the ground the retro-reflector 41 islocated, it is possible for the control to move the robot in such a waythat the retro-reflector 41 comes into the angle of view of the sensordevice, and the photo-detector receives a retro-reflecting light beamwhen the emanating light beam meets the retro-reflector 41. Once theretro-reflector 41 has in this way come into the angle of view, themethod of automatically positioning a robot with the sensor deviceproceeds in the following way.

In a first phase, the control of the robot receives from the computingcircuit the necessary information in order to set both the angularposition at the normal 49 and the length of the normal 49, that is tosay the distance from the optical center 44 to the retro-reflector 41,in such a way that the angle of view covers all the line group regionsof the mask, that is to say in the case of the example according to FIG.3, all four line group regions 6A, 6B, 6C, 6D. In other words, it is inthis case achieved that the pulses of the photodetector, whichcorrespond to the lines of these groups of lines, all occur in the timeinterval between t_(A) and t_(E). An earliest pulse, which begins at thetime t_(1A), and a latest pulse, which stops at the time t_(1E),correspond to the group of lines first scanned. An earliest pulse whichbegins at the time t_(2A), and a latest pulse, which stops at the timet_(2E), correspond to the group of lines last scanned.

How the operation continues in this first phase can be explained mostsimply if the optical center 44 is brought in a first stage to thecenter perpendicular of the overall length of the line group regions 6A,6B, 6C, 6D and in a second stage as close as possible to the line groupregions 6A, 6B, 6C, 6D.

For example, the robot is for this purpose moved initially only in thehorizontal until the time t_(M) corresponds to the equation t_(M)=1/2(t_(2E) -t_(1A)), achieving the effect that the angle bisector ofthe angle of view coincides with the center perpendicular of the overalllength of the line group regions, i.e. is congruent to it, and theoptical center 44 lies centered, initially only in the horizontal, infront of the line group regions 6A, 6B, 6C, 6D. Thereafter, the robot iscontrolled, still only in the horizontal, in such a way that the timet_(M) continues to correspond to the equation t_(M) =1/2(t_(2E) -t_(1A))and, in addition, the times t_(1A) and t_(2E) come to correspond to theequations t_(1A) =t_(A) and t_(2E) =t_(E), then achieving the effectthat the overall length of the line group regions fills the entire angleof view. Of course, the control receives the information necessary forthis continuously from the computing circuit.

In a second phase, the control receives from the computing circuit theinformation necessary to reduce the distance between the optical center44 and the retro-reflector 41, that is to say the length of the normal49, in such a way that the angle of view from then on covers only twoneighboring line group regions. Which regions these two neighboring linegroup regions are is selected on the basis of the coding of their groupsof lines and a corresponding default value in the control. They areexpediently neighboring line group regions in the center of the series,that is to say in the case of the example according to FIG. 3, the linegroup regions 6B and 6C, which are coded by the numbers 2 and 3,respectively, which are detected by the computing circuit. Of course,the optical center 44 in this case remains centered in the horizontal infront of the line group regions 6A, 6B, 6C, 6D.

With this approaching of the retro-reflector by the robot it isessentially intended to increase the angular values at which the variousbar codes of the mask 42 are seen from the optical center 44, andthereby increase the precision of the positioning. From then on, theonly diagonal line lying in the angle of view is the diagonal line 9BC,of which a point 43 is represented in FIG. 4

In a third phase, the control receives from the computing circuit theinformation necessary to move the robot, in this case only in thevertical, until the time at which the angular position of the light beamcoincides with the point 43 of the diagonal line 9BC, or the point 43 isscanned, which coincides with the time t_(M), achieving the effect thatthe optical center 44 is then also centered in the vertical in front ofthe line group regions 6B, 6C. During this time, the robot has not beenmoved in the horizontal, so that the angle of view continues to becovered only by the neighboring line group regions 6B and 6C and theoptical center 44 has remained centered in the horizontal in front ofthe line group regions 6A, 6B, 6C, 6D.

Consequently, the optical center 44 now lies centered in the horizontaland in the vertical in front of the line group regions 6A, 6B, 6C, 6D.

The computing circuit is thereupon in the position to calculate thecoordinates of the optical center 44 with respect to the center point ofthe line group regions 6A, 6B, 6C, 6D. In Cartesian coordinates, thecoordinate in the direction perpendicular to the retro-reflector 41 andto the mask 42 is given by the length of the normal 49, while in thedirections parallel to the retro-reflector 41 and to the mask 42 thecoordinate is equal to zero, because the optical center 44 is indeedcentered in front of the line group regions 6A, 6B, 6C, 6D (this is thevery simplification mentioned above). These coordinates, or theindividual coordinate actually to be determined are prepared by thecomputing circuit for use by the control as a position reference of therobot with respect to the retro-reflector and are passed to the control.From then on, the control of the robot is capable of making the grippermove automatically to the individual points of significance at themachine or device concerned, in particular the positions at whichmagazines are to be brought or picked up, and handle the variousmagazines in accordance with their type.

In general, there are two mutually equivalent possibilities of relatingthe local reference systems of the code carrier and of the scanningdevice to each other, namely by creating a direct relationship or anindirect relationship by means of a common system of coordinates or morethan one system of coordinates related to one another. On the one hand,in the scanning plane the angular position of the viewing directionabout the optical center may be related to a reference direction lyingin a predetermined angular position to the plane of the code carrier. Onthe other hand, the plane of the code carrier may be arranged in aposition predetermined in a system of coordinates, while in the scanningplane the angular position of the viewing direction about the opticalcenter is related to a reference direction of the angular positionpredetermined in the system of coordinates.

Preferably, however, all the calculations are simplified by thereference direction lying orthogonally to the plane of the code carrierand the displacements taking place in three mutually orthogonaldirections, of which one lies parallel to the reference direction andthe two others lie parallel to the plane of the code carrier.

For executing the method according to the invention, it would sufficefor the line group regions to lie in the angle of view, while, inprinciple, it is not necessary for the angle bisector of the angle ofview to coincide with the center perpendicular of the line groupregions. If the angle bisector of the angle of view does not coincidewith the center perpendicular of the line group regions, the opticalcenter of the sensor device is not centered in front of the line groupregions, whereupon the trigonometric calculation of the position of theoptical center in relation to the retro-reflector becomes morecomplicated and the computing circuit and the control becomecorrespondingly more complex, but the calculation and the correspondingdesign of the computing circuit and of the control remain within thescope of general technical knowledge and therefore need not be describedin detail. For example, the computing circuit may be designed as amicroprocessor and be correspondingly programmed.

For executing the method according to the invention, it would alsosuffice for the overall length of the line group regions to fill theentire angle of view, while it is not necessary for only two selectedline group regions to fill the entire angle of view. If no approachingof the sensor device to the retro-reflector takes place, the only effectis that the achieved precision of the position determination in thehorizontal and in the vertical as well is less than in the case of themethod described with such an approach.

Finally, for executing the method according to the invention it is notessential for the optical center 44 also to be centered in the verticalin front of the line group regions 6B, 6C. In general, the angularposition of the light beam at a certain time t_(H) coincides with thediagonal line 9BC, i.e. a point 43 of the diagonal line 9C is scanned atthe time t_(H). This time t_(H) varies linearly with the position of theoptical center 44 ill the vertical in front of the line group regions6B, 6C. It is assumed that the optical center 44 is centered in thehorizontal in front of the line group regions 6B, 6C, as described inthe text above, that is to say that the equation t_(M) =1/2(t_(2E)-t_(1A)) is satisfied. Under these circumstances, the time t_(H)coincides with the time t_(M) when the optical center 44 is alsocentered in the vertical in front of the line group regions 6B, 6C.However, the time t_(H) coincides with the time t_(1E) when the opticalcenter 44 lies in the vertical in front of the border last scanned ofthe group of lines first scanned, and coincides with the time t_(2A)when the optical center 44 lies in the horizontal in front of the borderfirst scanned of the group of lines last scanned. Consequently, thistime t_(H) varies linearly between the extreme values t_(1E) and t_(2A)in dependence on the position of the optical center 44, in the verticalin front of the line group regions 6B, 6C. A simple proportionalcalculation thus allows the computing circuit to calculate the positionof the optical center 44 in the vertical in front of the line groupregions 6B, 6C in dependence on the times t_(H), t_(1E) and t_(2A) andto prepare it for use by the control of the robot.

The preparation described of the information on the position of theoptical center of the sensor device in the horizontal and in thevertical in front of the line group regions, that is to say in front ofthe retro-reflector and the mask, and the passing on of this informationto the computing circuit makes it possible for the control of the robotto position itself, if appropriate, in front of other line groupregions, such as for example in front of the line group regions 4 or 5in FIG. 3, in order to read further information in these additional codefields. For example, the type of the machine or device on which theretro-reflector 1 is attached is coded on the retro-reflector 1 in theline group region 4, while a further line group region 5 can be used foradditional coded information. Moreover, one or more furtherretro-reflectors may be provided with additional code fields and bearranged ill a predetermined position in relation to theretro-reflector 1. Since the computing circuit is aware of thepredetermined position of these additional code fields in relation tothe code field of the retro-reflector 1, it is possible for the controlof the robot to go to these additional code fields without a precedingsearch, in order to read their information.

Consequently, a single scanning device suffices both for the initiallynecessary determination of the position of the mounting robot illrelation to the machines or devices and their magazine positions andthereafter for the reading of further code fields, which supplyinformation, for example, on the type of a machine, of a magazine andthe like. Because the mounting robot knows the positions of theadditional code fields as soon as it has learned the positions anddimensions on the machines or devices and on the magazines, it ispossible for it also to move to the further code fields and bring itselfinto the angle of view of the scanning device, in order to read theirinformation.

By the preparation described of the information on the position of theoptical center of the sensor device in the horizontal and in thevertical ill front of the line group regions, that is to say in front ofthe retro-reflector and the mask, and by the passing on of thisinformation to the control of a robot, it is possible, for example, tocontrol a mounting robot for a line of machines and/or devices, inparticular for the automatic processing, and/or of devices for theautomatic treatment of electronic chips in such a way that the correctmagazines are brought to the correct position of the correct machines ordevices and are picked up from these positions.

In the case of any one of these positioning operations, the computingcircuit of the sensor device and/or the control may also check whetherthe current set position coincides with the set position determinedearlier. If this is not the case, the machine and/or device concernedhas, for example, been displaced or otherwise changed, which, forexample, sets off an alarm.

In FIGS. 5a, 5b, 6a and 6b, in each case various variants of the designof the code in an interfield are represented as a geometrical diagram.The frame now represented diagrammatically corresponds in each case tothe interfield which has already been described in the above text inconjunction with FIG. 3, but there only with a virtual border, i.e. notrepresented by an actual line.

In FIG. 5a, for a better overview, the design which has already beendescribed in the text above in conjunction with FIG. 3 is representedonce again. A diagonal line crosses through the interfield, essentiallydiagonally and by section approximately into two interfield regions ofan optically identical nature. The diagonal line is dark and theinterfield regions are light (or vice versa), i.e. the diagonal line isoptically different from the interfield regions. Each of the twointerfield regions produces with the diagonal line a boundary line,which crosses through the interfield approximately diagonally; there areconsequently two mutually parallel boundary lines. The scanning deviceresponds to the optical contrast at the two boundary lines by thiscontrast producing in it a variation of the illumination density, whichleads to the determination of a viewing direction.

In FIG. 5b, a design which is derived from the design according to FIG.5a essentially by mirror-symmetrical duplication is represented, theinterfield being essentially bisected along the center line into twointerfield parts, and the diagonal lines of one interfield part and ofthe other interfield part lying at an angle to each other so as to bechevron-shaped.

In FIG. 6a, a design in which the interfield is essentially bisectedessentially diagonally into two optically different interfield regionsis represented. The one interfield region is dark and the other light,i.e. a boundary line crosses through the interfield essentiallydiagonally. The scanning device responds to the optical contrast at thisboundary line by this contrast producing in it a variation of theillumination density, which leads to the determination of a viewingdirection.

In FIG. 6b, a design which is derived from the design according to FIG.6a essentially by mirror-symmetrical duplication is represented, theinterfield being essentially bisected along the center line into twointerfield parts and the boundary lines of one interfield part and ofthe other interfield part lying at an angle to each other as to bechevron-shaped.

It is quite possible for there to be other designs of the code in aninterfield, in which the code in at least one interfield comprises atleast one a boundary line obliquely intersecting the center line betweentwo surface areas of the interfield, and the surface areas are designedfor the purpose of producing during the scanning of their commonboundary line by the scanning device in the latter a variation of theillumination density, which leads to the determination of a viewingdirection. In particular, it is to be understood that the drawingsrepresented in FIGS. 5a, 5b, 6a and 6b can be mirror-inverted about thetwo virtual center lines of their rectangles, i.e. in FIGS. 5a, 5b, 6aand 6b the terms "upper" and "lower" are interchangeable, and likewisethe terms "light" and "dark" are interchangeable, without departing fromthe principle of the invention.

In all the designs of the code described in the above text, the codefield preferably comprises an even number of positioning fields of thesame size as one another and a corresponding odd number, one less, ofinterfields of different sizes to one another, and the interfields areeither identical or mirror-identical to one another. In the preferreddesign according to FIG. 3 the code field comprises precisely fourpositioning fields and three interfields.

What is claimed is:
 1. A system for sensing the relative position of twomutually displaceable objects, comprising:an optical code provided in acode field of a substantially planar code carrier arranged on one ofsaid objects for displacement therewith; an optical scanner having afield of view which extends throughout a viewing angle relative to anoptical center, the optical scanner being equipped to detectillumination density and direction from said optical center for readingsaid optical code; said scanner being arranged on the other of saidobjects for displacement therewith; an illuminator for causing light tobecome incident on said code field; means for displacing at least one ofsaid objects relative to the other of said objects, and thereby causinglight which has become incident on said code field to become within saidviewing angle and detectable by said optical scanner; said field beingsubstantially rectangular, having a longitudinal centerline andincluding a plurality of fields arranged in a series extending alongsaid centerline and including at least one substantially positioningfield arranged between two substantially rectangular interfields; saidpositioning field containing coded information about the position ofsaid positioning field with respect to a reference point on said one ofsaid objects and about the identity of one of said objects; each saidinterfield including at least one boundary line between two areas which,when illuminated by said illuminator, can cause differing illuminationdensity to be detected by said optical scanner, said boundary linecrossing said centerline at an oblique angle thereto; and control meansoperatively interconnecting said optical scanner and said displacingmeans, for mutually positioning said two objects so as to provide adetermined relative position, based on differing illuminator densitydetected by said optical scanner as a result of illumination of saidboundary lines of said interfields by said illuminator.
 2. The system ofclaim 1, wherein:in each of said interfields, each respective saidboundary line is a diagonal line.
 3. The system of claim 1, wherein:ineach of said interfields, there are two said boundary lines which areoblique to said centerline and oppositely oblique relative to oneanother.
 4. The system of claim 1, wherein:each of said interfields isflanked by respective two said positioning fields, for a total of atleast three interfields and at least four said positioning fields; thecoded information contained by said positioning fields being related ina series which extends along said centerline.
 5. The system of claim 1,wherein:said one object is a processing line for electronic computerchips, and said other object is a robot for acting on computer chips onsaid processing line.
 6. The system of claim 5, wherein:said displacingmeans is operable for moving said robot in these mutually orthogonaldirections relative to said processing line.
 7. An information-providingtarget for use in locating a mobile robot relative to a station on anautomated processing line, comprising:a substrate mountable at a sitecorresponding to a station on the automated processing line; aninformation block comprising a series of groups of line patternsextending in a given direction corresponding to a scanning direction ofa sensor; said information block being affixed to said substrate; saidseries of groups of line patterns being constituted by a plurality ofpositioning fields alternating with a plurality of interfields; eachpositioning field comprising a plurality of parallel straight linesextending normal to said direction, within a notional rectangle, as tohave opposite line ends; each interfield being located between arespective two of said positioning fields and including at least oneline extending obliquely relative to said direction.
 8. The target ofclaim 7, wherein:said substrate is retro-reflective, and each said lineis opaque.
 9. The target of claim 7, wherein:each said interfieldcomprises a single line extending diagonally between opposite ends ofrespective most closely neighboring ones of said lines of respectiveadjacent ones of said positioning fields; said single line beingdisposed between two triangular non-lined areas which, together withsaid single line, fill a respective notional rectangle.
 10. The targetof claim 7, wherein:there are three said interfields.
 11. The target ofclaim 7, wherein:each said interfield comprises a pair of triangularforms sharing a hypotenuse which extends diagonally between oppositeends of respective most closely neighboring ones of said lines of tworespective adjacent ones of said positioning fields; one of saidtriangular forms having a substantially different degree of lightreflectivity or transmissivity than the other.
 12. The target of claim7, wherein:each said interfield comprises a chevron-shaped line composedof two line segments which meet at an apex located intermediate,relative to said direction, respective most closely neighboring ones ofsaid lines of respective adjacent ones of said positioning fields; saidsingle line being disposed in complementary alternation with thesetriangular non-lined areas, which, together with said chevron-shapedline, fill a respective notional rectangle.
 13. The target of claim 7,wherein:each said interfield comprises a series of three triangularareas, including two flanking triangular areas and one centraltriangular area, mutually bounded by a chevron-shaped interface and,together, filling a respective notional rectangle; said centraltriangular area having a substantially different degree of lightreflectivity or transmissivity than do said to flanking triangularareas.